Electric signaling system



Jmily 3,1923.

L. H. DARROW ELECTRIC SIGNALING SYSTEM Filed Jan. 30' 1920 llVVE/V T 01? Z. H flaw/m ATTOE/WY Patented July 3:, 1923.

LEO H. DARROW, OF NEW YORK, N. Y., ASSIGNOR T0 AMERICAN TELEPHONE AND TELEGRAPH GOIHPANY, A CORPORATION OF NEW YORK.

ELECTRIC SIGNALING SYSTEM.

Application filed January 30, 1920.

To all to 7mm it may concern Be it known that 1, Leo H. DARROW, residing at New York, in the county of New York and State of New York, have invented certain Improvements in Electric Signaling Systems, of which the following is a specification.

This invention relates to electric signaling systems and more particularly to a busy test arrangement connected with the operators telephone set of a cord circuit adapted for use with the said signaling systems.

In the busy test circuit heretofore used having an operators telephone set common to all the cord circuits of a particular position, it has been customary to employ a single relay in the busy test lead of the telephone set. This relay was designed to operate whenever the tip of a plug of a cord was brought in contact with an energized sleeve of a jack connected with a busy line. As is well known it is customary to terminate a line in a plurality of jacks into any of which a plug of a cord circuit might be inserted, and the insertion of a plug into one of the jacks raises the potential of all the sleeves of the jacks connected with the same line. When the tip of a plug is brought in contact with one of the sleeves, current will flow over the tip conductor of the cord circuit and through the winding of the relay associated with the busy test lead, which results in the closing of a local circuit whereby current of the desired magnitude flows through the receiver of the operators telephone set. Trouble has been experienced in maintaining the said relay so accurately adjusted that it will close the local circuit whenever and as often as the tip of the plug is brought in contact with the sleeve of a jack of a busy circuit. One of the objects of the present invention is to provide a busy test system which does not require the use of a relay to close the local circuit through the operators telephone set, thereby avoiding the maintenance and oper ating difliculties which have resulted from the use of such a relay.

Another object of this invention is to provide a busy test system having such impedance to the flow of current that a marginal relay associated with the sleeve contact of Serial No. 355,173.

said jacks, and controlled by the cord circult that is connected with one of said jacks, will not be inadvertently released by the diversion or current through the busy test circult of other cord circuits when a plurality oi busy tests are made substantially simultaneously.

The objects of the invention and the in vention itself will be made clear from the following description of the invention when read in connection with the attached drawing, which shows one embodiment of the in vention.

In the drawing L represents a telephone trunk line extending from an otllceA to another oliice or a private branch exchange B, terminating therein in a plurality oi jacks J J and J At the oflice B is a cord circuit X of a well known type which terminates in the plug P adapted for insertion in the jack J and in the plug P which may be inserted in the jack of a subscribers line orother signaling circuit. X and X represent only the busy test circuits of two cord circuits similar in this and all other respects to the complete cord circuit X, which terminate in the plugs P and P adapted for insertion in any of the jacks J J or J but are shown associated with jacks J and J in order that the obyects of this invention may be made clearer. The cord circuit X has associated therewith an operators telephone set T which is adapted for connection with the tip and ring side of the cord circuit by the op eration of the listening key K The telephone set T has associated therewith a re celver-R which is connected in series with one of the windings of the induction coil 1. Another winding or said coil is connected with the transmitter to which current is supplied by the operation oi the key K Bridged across the receiver R, is one of the windings of the transformer 2, the other winding of said transformer being connected in series with the condenser G which is in turn connected by means of the conductors l, 5, and 6 and a contact of relay R with the tip contact of the plug P A resistance 7 the mag nitude of which is preferably fairly high is connected in parallel with the condenser C in order to effect the discharge of the said condenser. in the circuits X and X are shown the details of the busy test arrangement which has just been described in con nection with the cord circuit. Associated with the cord circuit X are the relays R and R,, which are designed when operated to connect together the tip conductors of the two cords of the circuit, and to disconnect the conductor 5 from the tip conductors of the cord circuit. Associated also with the cord circuit X are the supervisory lamps S and S and the relays R and R respectively which control the operation of the said lamps.

Associated with the line L at the office A is a cord circuit comprising source of talking current B, which is connected to the line L whenever the plug P oithe cord circuit is connected with the jack J ot the line L This cord circuit at A has associated therewith a source of ringing current Gr by means of which signals may be transmitted to the terminal l3. Associated with the line L, at the otlice B are the relays R R R R R and an impedance coil 8. Also associated with the line L, is the lamp S which responds to signals transmitted from A to B.

This invention will be better understood from the following description ot the method of its operation. It the cord circuit at A is connected. with the line'li, by the insertion of plug P in jack 5 and ringing current is applied to the ring side of the line L by the operation of generator G the ringing current will pass through the condenser 9, contact '10 and winding of the relay P contact 11 ot' the relay R, to ground, causing the operation of the relay R By the closing oi: the contacts of relay It current will flow from the battery B one winding of relay R contact 12 of relay R winding of relay R contact 11 of relay R to ground, thereby locking relays R and The lamp S, will be lighted by the flow of current from battery 3,, lamp 5,, conductor 13, contact 1% of relay R and one of the windings of the marginal relay R to ground. Upon the lighting ot' the lamp S the operator at B inserts the plus P, of the cord circuit X in the contact 1 with the listening key K in its operated po sition. This operation results in the flow of current "from the battery B, associated with the key K over conductors 16 and 17, the winding of relay R sleeve contacts of the plug P, and jack J, and through the complete winding of relay R to ground, causing the operation of relays 3 and it the latter of which closes its contact 18 and thereby causes the operation of relay R When the right hand armature of the relay R, operates, the ground is removed from the winding of the relay 1% which thereupon is restored to its normal unoperated position, and contact will be closed. It should be noted that the potential of the battery B at oilice A is applied across the line L at all time except when the ringing key of the same cord circuit is operated. Therefore, when contact 19 of relay R, is closed, current will flow from the said battery over the tip side of line L, to point 26 thence through contact l9, the series contacts oi keys K K and K throu h the impedance coil 8 and winding of re ay R to the ring side of the line thereby causing the operation of the relay R which, by the opening of its contact 20, causes the release of the marginal relay When the line L has been connected to the desired subscribefs line by means of the cord circuit 2; the sleeves of the jacks J and J which are located at different switchboard positions ironi that in which the jack J located, will be energized by current from the battery l}, associated with the cord circui X, t the operators at the positions in which the jacks J and ii are located desire to use the trunk L, they will first make the usual busy test upon the said line. which consists in touching the tip oi the plug of a cord circ it to the sleeve of the jack oi the desired line. lVhen the operator at the position which jack J is located touches the tip oi the plug P to the sleeve of the jack J the flowot' current will take place from the sleeve oi the said jack to groimd, thereby charging the condenser C The charging of this condenser causes a ilow of current in one of the windings or" the transformer 2], which connected in series therewith, which induces current in the other winding, which produces a click in the receiver of the operators telephone set. By means of the resistance 23, which is connected in parallel with the condenser C the condenser O, may be discharged, and is left in condition to be charged again when the tip of the plug is brought contact with the sly-ere of the jack J This arrangement provides a simple ausy test circuit, which requires no reh s in its operation, and which may therefore be readily maintained and operated since it has no moving parts requiring adjustment. It will also be seen in this particular form of busy test circuit that it is only necessary to bring the tip of a plug in contact with the sleeve oi the desired jack in order to make the busy test, thereby avoiding' the necessity of operating any keys of the switches. Furthermore, since the receiver of the telephone set is inductivcly related instead or being directly connected with the busy-test lead, the telephone circuit is insured against impairment it the busy test circuit becomes detective.

A further object of the invention is to prevent the release of the marginal relay It, when a busy test is made for example uponjacks J and J, by the cord circuits in those positions after the plug P, has been inserted in jack J, in response to a call over line L 11' the operator at the ofiice A desires to signal the operator at B after the line L, has been connected with another line at the oilice B by means of the cord circuit X, she performs some act which opens the circuit previously traced from battery B, through the winding of the relay R such as operating the ringing key or withdrawing the plug P, from its jack. This causes the release of the relay R which by the closing of contact 20 allows current to flow from the battery B through the right hand winding of the marginal relay R contact 20 and the right hand contact 25 of relay R, to ground. Relay R is thereby operated and by the closing of its right hand contact a circuit is established from battery 15 conductors 16 and 17 to point 28 where the circuit divides, part of the current passing through winding of the relay R and part through the lamp S in parallel therewith, thence through the sleeve contacts of plugs P, and jack J part of the winding of the relay R contacts of the relays R, and R and the left hand winding of relay R, to ground. Suflici-ent current therefore will flow to cause the lamp S to light, which in dicates to the operator at B that theoperator at the office A is signaling to her. It the operator at B notices this signal prompt- 1y, she will operate the listening key K which bridges her telephone set across the conductors of the cord connected with the line L,. This operation of key K opens the circuit through the lamp S at the contact 27 of key K thereby increasing the re sistance of the circuit through the marginal relay R, to such extent that the relay R fails to receive suificient current to main tain it in its operated position, and it is accordingly restored to its normal position. When the operators at the positions in which jacks J and J, are located touch the tip contacts of the plugs P and P to the sleeves of the jacks J and. J respectively,

not be noticed by the operator at the latter oiiice, and delay and confusion would thereby result. By making the resistance of the busy tests circuits of proper magnitude based upon study of operating conditions,

the possibility of releasing the marginal relay it, before the operator at B has responded to the signal of the lamp L1 may be considerably minimized if not entirely that it is not limited to this single term,

but is capable of embodiment in other and different forms within the scope of the appended claims.

lVhat is claimed is I 1. In a signaling system, the combination with a line circuit terminating in a plurality of multicontact jacks, of a marginal relay having one winding effectively connected with the sleeve contacts of the jacks at one end oi said line circuit, a cord circuit having a supervisory signal and a source of current also connected with the sleeve contacts of thesaid acks to which the said: marginal relay is connected, whereby the said relay may be locked up, a plurality of other cord circuits having busy-test branches connected with the tip conductors thereof, the electrical constants of which branches are so proportioned as to prevent the release of the said marginal relay when a predetermined number of busy tests are simultaneously made.

2. In a signaling system, the combination with a line circuit terminating at one end in a line jack and at the other end in line and multiple jacks, the sleeves of which are electrically connected together and the tip and ring contacts being connected to the line conductors, a cord circuit having multicontact plugs for connection with the line j aclc at one end of said line circuit, a second cord circuit having multicontact plugs ifor con nection with the line jack at the other end or said line circuit, and the said second circuit also having a supervisory signal and a source of current connected in the sleeve conductor thereof, a bridged relay and a marginal' relay connected with the said line circuit, the said bridged relay being controlled by the said first cord circuit, and the margi nal relay being controlled by the said bridged relay-and having a winding connect-- ed with the sleeves of the said line and the said multiple jacks, whereby the said relay may be locked up, and. the said signal operated by current from the said second cordL circuit, and a plurality of other cord circuits having plugs for connection with the said multiple jacks and arranged for the making of busy-tests upon the said line circuit by touching the tips of the said plugs to the sleeves of the said jacks, the said busytest circuits having their electrical constants 5 so chosen with respect to the constants of the marginal relay that the latter will not he released by the making of a predetermined number of busy-tests simultaneously upon said line circuit.

In testimony whereof, I have signed my 10 name to this specification this 28th day of January 1920.

LEO H. DARROVV. 

